Field of the Disclosure
The present disclosure relates to a display device, and more particularly, to a transparent adhesive composition, a transparent adhesive layer, and a display device including the same. Although the present disclosure is suitable for a wide scope of application, it is particularly suitable for improving adhesion property and optical property of a display device including a transparent adhesive layer.
Description of the Background
As information technology and mobile communication technology have been developed, a display device capable of displaying a visual image has also been developed. Flat panel display devices, such as a liquid crystal display (LCD) device and an OLED device, are developed and used instead of a cathode ray tube (CRT).
To prevent damages on the display device from an external impact, the display device includes a cover glass on a display surface.
FIG. 1 is a schematic view of the related art display device.
As shown in FIG. 1, the display device 10 includes a display panel 20, a cover glass 30 disposed over a display surface of the display panel 20 and a transparent adhesive layer 40 between the cover glass 30 and the display panel 20. The cover glass 30 and the display panel 20 are attached by the transparent adhesive layer 40.
The display panel 20 may be a liquid crystal panel or a light emitting diode panel.
For example, the display panel 20 as the liquid crystal panel includes first and second substrates facing each other, a pixel electrode and a common electrode generating an electric field, a liquid crystal layer between the first and second substrates and first and second polarization plates at an outer side of each of the first and second substrates.
In this instance, the cover glass 30 is attached onto the second polarization plate at the outer side of the second substrate using the adhesive layer 40. Accordingly, the display panel 20 is protected by the cover glass 30 such that the damages on the display panel 20 can be minimized.
For example, the transparent adhesive layer 40 is formed of an urethane acrylate compound. However, the transparent adhesive layer 40 of the urethane acrylate compound is very weak under high temperature and humidity condition.
In the high temperature condition (e.g., about 105° C.), a yellowish problem of the transparent adhesive layer 40 can be generated. In addition, in the high temperature and humidity condition (about 85° C., 85%), a haze value of the transparent adhesive layer 40 can be increased and the transparent adhesive layer 40 can be partially melt.
Namely, when the transparent adhesive layer 40 of the urethane acrylate compound is used at the high temperature and high humidity conditions, a free volume is strongly or rapidly increased such that moisture is penetrated into the free volume. As a result, optical, chemical and physical properties of the transparent adhesive layer 40 are deteriorated.
On the other hand, to overcome the weak heat-resistance property of the urethane acrylate compound, a silicon acrylate compound is suggested to form a transparent adhesive layer. A bonding energy of Si—O in the silicon acrylate compound is greater than a bonding energy of C—C and O—O in the urethane acrylate compound, so that the silicon acrylate compound has the heat-resistance property being better than the urethane acrylate compound.
However, the adhesion property (or strength) of the transparent adhesive layer of the silicon acrylate compound is worse than the transparent adhesive layer of the urethane acrylate compound. Accordingly, a peeling problem of the cover glass may be generated.